Various appliances have been suggested which include a device for forming a trench having substantially vertical side walls in the ground, and for laying strand-like material of endless length, such as conduits, pipes and cables, into the trench. It should be noted that “endless length” designates a material which is very long in comparison with the length of the device laying the material, and does not require that the material be of infinite length. Such appliances are described e.g. in WO 86/00536 A1, U.S. Pat. No. 3,747,357, U.S. Pat. No. 3,486,344, U.S. Pat. No. 3,486,344, U.S. Pat. No. 3,429,134, DE 1 189 602 A1, DE 32 45 625 A1, DE 25 29 285 A1, DE 28 06 379 A1 or DE 491 887 B1 and typically comprise a support vehicle, a blade connected to and supported by the support vehicle for lifting and lowering, and a feeding means mounted in connection with the blade for pivotal movement about a horizontal axis and feeding the strand-like material from a storage reel rotatably mounted on the support vehicle, through an internal guide channel into a subterranean trench formed by the blade immersed into the ground when moving the support vehicle. With such appliances, in a single step a vertical trench can be formed in the ground and a strand-like material can be fed into the trench and laid onto the base of the trench while the support vehicle is moved forwardly.
The above mentioned appliances are designed for laying a strand-like material of relative high flexibility, such as cables, wound on a storage reel. However, such appliances are not appropriate in cases where strand-like material of relatively low flexibility and of “endless” length, such as more rigid steel pipes like gas pipes, oil pipes, etc., are to be laid. Normally, strand-like material of the latter mentioned more rigid or less flexible type is not fed from a storage reel but rests on the ground surface prior to being laid into the ground and is picked up, fed along a curved path into a trench formed in the ground by the appliance. In order to reduce a risk of being damaged or broken due to failing below a minimum allowable bending radius of the strand-like material of the more rigid or less flexible type to be laid, the curved path must be set so as to assure a sufficiently large radius of curvature, so that the length of the known appliances becomes very large if more rigid strand-like material is to be laid into the trench.